Industrial computed tomography (CT) scanning technique provides an effective laboratory technique for the analysis and study of internal structures of materials and is widely used in various related fields.
A conventional industrial CT generally uses X-rays to penetrate a section of an object, and performs a rotational scan, to reconstruct an image of the internal part of the object by means of a high-performance computer system. The principle is described as follows. The intensity of X-rays after penetrating the object to be detected is measured by a specific detector, and in the meantime, a scanning action among the X-ray machine, the detector and the object to be detected is performed, thus obtaining complete data required for reconstructing a CT image, and finally, the image of the section of the object is reconstructed by using these data based on a certain algorithm.
However, due to essential characteristics of the industrial CT scanning technique, to obtain a better resolution, in one aspect, the size of a focus of the ray beam is required to be reduced as much as possible, to restrict the penetrating ability of the rays; and in another aspect, the size of the sample should be carefully restricted and a stable rotation of the sample during the scanning should be guaranteed, to restrict the dimension of an object to be scanned. These restrictions adversely affect the application of the CT technique in mechanics analysis to a great extent. A loading device is indispensable in mechanics experiments; however, a conventional loading device generally has a large volume and weight, and is hence difficult to be directly placed in the industrial CT machine to be used in the scanning process. Therefore, in the conventional technology, loading is generally performed outside of the CT machine, and then the loaded sample is placed on a test-bed of the CT. This loading method has a low accuracy, and once the loading is finished, the load applied to the test sample is not adjustable.
For homogeneous materials such as metal, rubber, and ceramic, a small sample and a miniature loading device may be used for the scan and analysis, which may ensure that rays are able to penetrate the sample to form an image, and the image can meet the requirement for a certain resolution ratio. However, for the analysis of the mechanical loading performed on a geotechnical material, the following challenges should be overcome. Firstly, the sample cannot be too small; otherwise, the analysis may be influenced by a dimensional effect such that a desired experimental result cannot be obtained. However, the increase in the size of the sample may inevitably result in the increase in the size of the loading device, thus causing a series of issues such as, rays are difficult to penetrate the sample, the loading tonnage is increased, and the resolution ratio of the image is decreased. Secondly, loading schemes are generally complicated; to simulate a stress state of the geotechnical material in practical engineering, a simple uniaxial tensile and compression experiment is not sufficient, various complicated loading experiments are further required, such as multi-axial compression experiment, percolation experiment, and hydraulic fracturing experiment. Also, sometimes loading and unloading procedures are required to be performed many times. Hence, a higher requirement is imposed on the implementation and control of the loading device.
Therefore, a technical issue to be addressed by those skilled in the art is to provide an industrial CT scanning test system, which can realize multi-directional loading on a sample, to meet test requirements.